There is an extension that adds compression. [0] I think most widely-used servers implement it (at least Gmail and Dovecot do) [0] https://www.rfc-editor.org/r

There is an extension that adds compression. [0] I think most widely-used servers implement it (at least Gmail and Dovecot do) [0] https://www.rfc-editor.org/rfc/rfc4978.html https://www.rfc-editor.org/rfc/rfc4978.html